Doggy doors question

I’ve never had a door with a doggy door in it but I’m considering installing one for my 2 yr old.

My questions are for those that do have one, how off the floor is yours installed so your pupper can easily go through and not compromise the strength of the door. Which type do you have: the french door type or the more traditional swinging flap type. And lastly how difficult was it to train them to use it.

Thanks for the responses ☺️